This invention relates to the field of computer programming and data processing systems for processing a service request relating to any locally switched telecommunication service using improved nondesign systems and processes. The service request can relate to installation, maintenance or repair of any analog or digital locally switched service such as Plain Old Telephone Service (POTS), coin and special services. The invention also finds application when processing service requests relating to field cable throws. Scheduling of appointments based on availability of outside technicians is more efficient and accurate using the system and method of the invention. The invention utilizes line conditioning equipment that is installed at a customer premise which provides a stabilized loop loss within a desired range, line balancing and slope equalization at the customer premise based upon the requested service.
The widespread advantages of the invention are better appreciated by examining the drawbacks of prior art telecommunications systems and methods for processing service request relating to prior art designed services provided across transmission equipment extending between a telecommunications company central office (local serving office) and a customer premise (i.e., a local loop). The local loop consists of outside plant facilities including feeder plant facilities or cables, distribution plant facilities or cable, conduit, poles, cable protection devices, terminals and drop wire that allow for signal transmission between the central office and the customer premise. The feeder plant facilities typically extend from central office and terminate at a remote switching module, or hub such as a pair gain system. The distribution plant then extends from the feeder plant termination either to a terminal located inside the customer premise or to an outside terminal disposed in close proximity to the customer premise. Drop wires connect the outside terminal to the customer premise. The transmission equipment associated with the feeder and distribution plant can be, for example, two or four wire copper facilities, coaxial cable, or optical fibers. The feeder plant also may include multiplexing equipment that allows for a number of signals to be multiplexed (e.g., using frequency division multiplexing for analog signals or time division multiplexing for digital signals) into a single transmission medium such as copper, coaxial cable, or optical fiber. The local loop is also referred to as a transmission circuit, channel, line, link or trunk.
In general, public telecommunication networks employ carrier-provided switching systems located in various switching offices to connect, or switch, signal transmissions carried on a first local loop to signal transmissions carried on another local loop. A local serving office connects directly to each local loop. A tandem office connects several local offices. Toll offices are used to switch long-distance or toll circuits between distant cities or geographic areas, and connect various tandem offices and/or local central offices.
Traditionally, the local loop is often the weakest link in the public telecommunication network since it is most susceptible to transmission impairments. As a signal travels outbound from the central office and progresses along the cable pair toward a customer, its power is reduced or attenuated by losses in the cable pair. Loop loss generally is due to dissipation, or reflection due to an impedance mismatch, or both. Other factors that inhibit the successful signal transmission across a cable pair include attenuation as a function of frequency or signal level; crosstalk; echo; transients based on impulse noise, gain hits, phase hits, and dropouts; thermal noise; intermodulation distortion; delay distortion; phase and amplitude jitter; and frequency errors. As the length of the cable pair needed to connect the central office and network interface at the customer premise increases, the likelihood for any particular local loop to have excessive unacceptable losses or transmission impairments also increases.
Therefore, design and testing of local loops has been very important in the telecommunications industry to ensure the loop loss associated with the circuit extending from the central office to the customer premise is maintained within an acceptable range at the network interface for the telecommunications service provided. For example, when certain analog services such as network data lines, local two-way PBX trunks, and PLEXAR.RTM. (registered trademark of Southwestern Bell Telephone Company) or CENTREX.RTM. central office lines (prior art designed services) are provided across the cable pair, the acceptable range of loop loss is 4 to 41/2 dB at the network interface. For POTS, the acceptable range of loop loss at the network interface is 8 to 81/2 dB. Additionally, for high speed data transmission, it is very important that the cable appear uniform and balanced to the signal traveling down it. Any discontinuities, impedance mismatch or irregularities will cause reflection losses and echoes which prevent proper signal transmission. To provide balanced lines and minimal reflective losses for special service data transmission, published tariff standards require that the loop loss not exceed 41/2 dB.
In the prior art, if an excessive unacceptable loop loss is measured by a technician at the network interface for POTS, a standard or pre-designed amplifier is typically installed at the central office to boost the signal as it emanates from the central office. To provide a lower loop loss for special services and data transmission, a complex prior art design system and method discussed more fully in the prior art section of the DESCRIPTION OF THE PREFERRED EMBODIMENT section hereof is employed. The associated design review process typically requires a design engineer to carefully examine the loop resistance and capacitance of the pair to establish the loop characteristics, and design a customized amplifier or office repeater for installation at the central office to boost the signal to a sufficient level to overcome the excessive unacceptable loop loss and provide impedance matching, equalization, and signal regeneration (of received signals only). If the amplifier or repeater installed at the central office does not provide sufficient amplification of the signal to overcome the unacceptable loop loss, line repeaters or load points are installed at various locations along the local loop in an attempt to further amplify the signal to overcome the transmission impairments, provide timing and equalization, and restore the signal, if necessary.
Drawbacks to using amplifiers and office repeater bays at the central office to boost the analog signal include the fact that the amplifiers and repeaters occupy considerable space at the central office, and often require elaborate cooling mechanisms to keep the circuitry within safe operating temperatures. If the circuitry associated with the amplifier becomes "hot" or overdriven such that an insufficient loop gain/loss is present, a squealing, hissing or singing sound may be heard by the customer over the telephone line. The quality of transmission also can be impaired by noise associated with extraneous unwanted signals appearing in the transmission path between the central office and the network interface. Because many wires runs in a bundle within a single paired cable, the signal is susceptible to leaking electric signal from adjacent wires resulting in crosstalk. Crosstalk occurs when unwanted inductive, capacitive or conductive coupling occurs between any two communication paths. Increasing the amplification at the central office and mixing voice and data signals in the same cable bundle increases the probability of, and the amount of, crosstalk.
Furthermore, as will be discussed below in the following DESCRIPTION OF THE PREFERRED EMBODIMENT, it typically takes at least three to five business days to process a service order using the prior art design processes and install a customized amplifier at the central office. Moreover, installation, repair and maintenance of prior art designed services requires a disproportionately large percentage of the telecommunication company's available work force when compared to prior art nondesigned services. For example, a telecommunication company often processes over twenty million service requests relating to prior art nondesigned services a year, while processing less than one million service requests relating to prior art designed services during the same time frame. Of those service requests relating to prior art designed services, roughly 60% are for locally switched services, with the remaining 40% relating to private lines that are not locally switched. While the number of service requests relating to locally switched designed services is relatively small when compared to the total number of service requests typically processed, a disproportionately large number of personnel and computer systems are involved in a complex and cumbersome prior art design process to satisfy these service requests. Therefore, it is desirable to have a system and a method for processing a service request whereby the service request can be completely satisfied within a reduced time after receiving the customer request, preferably within several hours. It is further desirable that such a system and method provide a more efficient and accurate process for scheduling dates and appointment times for installation of a new service based upon availability of qualified technicians.
Installation of amplifiers and repeaters at the central office and the line repeaters and load points along the cable pair results in increased capital investment costs as well as maintenance costs. Since amplifiers, repeaters and loading coils also amplify noise, the line repeaters or loading coils conventionally are placed close enough together so that the signal itself is available for amplification, and does not become so weak as to be lost in the noise between amplifiers. Repeaters and loading coils are typically housed in apparatus cases located in either manholes or on poles. To insert a loading coil along a cable pair, it is necessary for telecommunications company employees to dig up the cable, or access the cable through a manhole or on a telephone pole. The employees then physically insert the repeater or loading coil in the cable. If 25 cable pairs are contained in the paired cable, typically all 25 pairs are loaded by the single loading coil inserted on the cable, even if only ten cable pairs actually are used for analog signal transmission. On the other hand, repeaters often are inserted only on a portion of the cable pairs in the cable. As a result, when a cable is dug up to install a repeater on one cable pair, it may be necessary to dig up the same cable pair just one or two months later to put a repeater on another cable pair in the same cable. Occasionally, a loading coil is installed in the wrong loop. Furthermore, digging up the cable requires considerable time and expense and often interferes with traffic flow, since most cable pairs are accessed through manholes located in the streets and sidewalks throughout a city.
Another significant drawback associated with using loading coils along a cable is that the loading coil must be removed should a loaded cable pair later be used for digital signal transmission. Digital signals are effectively destroyed when they pass through loading coils, since the induction added by the loading coils severely distorts the digital signal. Whenever a customer wants to convert a subscriber loop to provide digital signal transmission instead of analog signal transmission, the cable pair must be dug up and unloaded (i.e., all bridge taps, load coils, boosters, build out capacitors, and cable stubs are removed) to allow for digital signal transmission. If a new customer moves in, or the existing customer's needs change, such that digital transmission is no longer desired on this cable pair, the cable pair may need to be dug up to reinsert the loading coils or boosters to allow for analog signal transmission at an acceptable loop loss. Similarly, digital regenerators or line repeaters must be removed from a line when a line used for digital signal transmission is converted to allow for analog signal transmission. This creates a circular problem, where one cable pair may be repeatedly dug up to remove or insert loading coils, since digital signal transmission requires the cable pair to be unloaded while analog signal transmission requires the cable pair to be loaded.
Furthermore, the prior art methods and systems for transmitting analog signals across a cable pair are not suitable for networks that are digital from end to end. Totally digital systems require nonloaded outside plant distribution facilities to transmit the digital signals. Therefore, to accommodate digital networks, it is desirous to develop a telecommunications system and method that allows for installation of analog service on unloaded cable pairs so that the cable pair can be easily converted to allow for digital signal transmission at a later time, if necessary. It is also desirable to have a system and method that allows for a subscriber loop to be readily used for either analog or digital signal transmission, without requiring reconfiguration of the cable pair.
In certain exceptional situations in the prior art associated with special service arrangement requests for business customers, a customer powered amplifier with manual balance sold by Wilcom, a subsidiary of NAI Technologies, Inc., has been installed inside the customer premise to maintain the loop loss of the local loop within a acceptable range based upon the class and grade of service provided. When such a unit was used in the prior art prior to divestiture of AT&T, it typically was installed on the customer side of the network interface for remote customer stations connected to a PBX. The prior art Wilcom device is a 400 mechanics circuitry card which requires installation of special slotted shelves such as standard 400 type mounting shelves inside the customer premise for mounting the circuitry card therein. Drawbacks associated with the prior art Wilcom device include that local customer provided alternating current (AC) power is required for operation of the Wilcom device, and it must be mounted inside the customer premise since it does not have a weatherproof construction. TelLabs has developed a similar circuitry card that can be installed in this type of situation for business customers to provide amplification, equalization and impedance matching; however, the TelLabs unit has the same drawbacks of requiring customer provided AC power, and expensive and time consuming special mounting equipment for installation inside the customer premise. In addition, the Wilcom and TelLabs units require a technician to travel to the customer premise each time the characteristics of the local loop change to reset the units. The units must be manually reset to adjust to compensate for changes in the loop loss when the characteristics of the loop change (e.g., when a cable throw is performed). Furthermore, these types of units are not suited for installation at a residential customer premise.
Therefore, it is desirable to develop a telecommunication system and method that allows for installation of improved line conditioning termination equipment at the customer premise that maintains loop loss within a desired range based upon the class and grade of service and provides for slope equalization, impedance matching and line balancing. Such improved equipment is powered by a direct current (DC) power source located at a telecommunications company central office via the local loop, and does not require local customer AC power for operation. It is further desirable that such equipment has a weather-proof construction to allow for installation outside the customer premise. Such a device should be suited for installation at both residential and business customers. It is desired that the weatherproof unit should have dimensions that allow for installation of two units inside a Keptel.RTM. SNI-4600 Network Interface Box (sold by Keptel, Inc.) for residential customers. It is further desirable that such a line conditioning termination device is fully automatically resettable for any off hook condition so that a technician does not have to travel to the customer premise to reset the unit when the characteristics of the local loop change.
Moreover, it is desirable to develop a system and method for processing service requests relating to the installation, maintenance or repair of locally switched circuits on which such improved line conditioning termination equipment is or may be installed that does not employ prior art design systems and processes, but instead uses improved nondesign systems and methods to process all such service requests.
It is further desirable that such a system and method can accommodate service requests relating to either analog or digital locally switched services. For digital services, telecommunications companies may utilize digital network channel terminating equipment (NCTE) installed on at the customer premise and central office equipment to provide the requested digital service at a desired speed or baud rate. The NCTE is typically designed or modeled by a design engineer using prior art design systems and methods discussed in the DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT to regenerate the signal and provide the desired loop loss at the network interface. An improved digital line conditioning termination equipment can be installed at the customer premise to eliminate the need for the NCTE. In this regard, it is desirable to employ digital line conditioning equipment at the customer premise that regenerates the digital signal received at the network interface to correct signal distortion that occurs during transmission, and provides a stabilized loop loss within a desired range at the network interface without requiring any digital repeaters at the central office or along the line, or NCTE. The preferred system and method should be able to distinguish and separately track analog or digital equipment when processing an associated service request.